The Greenland ice sheet
What happens when there’s nothing left to melt?
In years past, when it rained near Greenlander Toennes Berthelsen’s family camp, water would flood down as the mountain top ice melted, creating rivers where there usually are none.
Last week, when it rained there, there was no river at all.
“It was heavy raining, but we couldn’t see any flood coming down,” Berthelsen said. The ice cap at the top of the mountain was completely gone.
It’s been exceptionally warm in Greenland this year.
Now, the same heat dome that cooked Europe is forecast to raise temperatures in Greenland into the 70s Fahrenheit on parts of the coast, and the ice sheet is in the midst of one of its most extreme melts on record, said Xavier Fettweis, a climate researcher at the University of Liège. On July 30 and 31, more than half of the ice sheet had at least some melting at the surface, Denmark’s research institutions reported on Polar Portal.
“The current melt rate is equivalent to what the model projects for 2070, using the most pessimistic model,” Fettweis said. That melting has global implications—if Greenland’s ice sheet were to melt entirely, it would result in about 20 feet of global sea level rise.
Again, it looks as if it’s all going to happen a lot faster than was predicted.
Both Fettweis and Mottram said the extreme melt happening now is something that climate models have not done a good job accounting for.
“By mid to end of the century is when we should be seeing these melt levels—not right now,” Mottram said. “[The models] are clearly not able to capture some of these important processes.”
Keep a packed bag by the door.
The trouble with all of this kind of modeling is that we’re just really bad at nonlinear modeling. So we linearize everything. The language of the model descriptions betray this, things like “at the current rate of melt, …”; the problem is, the “current rate” is changing. The rate of change of the rate of change is nonzero. So extrapolating from the first derivative of what we see today leads to conclusions of “in the year 2070” when was is actually going to happen is that we’ll see the damage next year, not fifty years from now.
Well, and it’s not just the problems with nonlinear modeling. It’s also the fact that most of our models tend to err on the conservative side. There are good reasons for that, but in this case, perhaps a bit too conservative in the estimates.
And there’s always a bunch of stuff we didn’t think of until it happens. Or that some people did think of and nobody really listened. For example the feedback loop of forests not recovering is obvious in hindsight and I’m sure some people have been screaming about it for decades but it’s only when it’s too late and a few other people say “uh…. yeah…. you were kind of right” that most people even hear about it. A few more decades at best until anyone does anything about it.
In my field of computer science we think we’re really good at modelling stuff. We really aren’t. Why do you think we have planes falling out of the sky all the time, for goodness’ sake? There’s the Boeing 737, of course, and the Airbus A350 has to be rebooted every 149 hours of flight time because otherwise random severe things will start to go wrong, from loss of redundancy to vital front line systems. And everyone treats this as normal, like having to turn your PC off and on again every so often. We can’t even properly model the computer system we’re building, for goodness’ sake, let alone what’s going on with the actual hardware, mechanics, turbulence and so on.
And these systems are nowhere near as complicated as climate systems. It’s hardly surprising that we’re constantly finding out that things are worse than we thought. The problem is that enormous numbers of people seize any deviation between the model and reality as proof that climate change is a lie and we should burn as much fossil fuel as possible to stick it to those uppity scientists.
Ditto everything that Latsot just wrote.
If people in general really knew how little “we” know about the world, and modeling it, they would be shocked and incredibly afraid, given the headlong rush that our species is making towards the cliff’s edge. It’s like we’re driving a car with the accelerator floored and all we get are brief glimpses out ahead.
And we’re still doing things that imply an indefinite future. PBS still runs NOVAs that talk about future space exploration plans, as if everything were just going to trot along smoothly forever.
One thing that annoyed me in the 90s (and still is heard occasionally today) was how good the increased carbon dioxide would be for plants. As a botanist, I am aware that most plants are not limited by the amount of carbon dioxide, but by (1) nitrogen; (2) phosphorus; (3) water; or (4) any combination of the above. Increasing the carbon dioxide in the atmosphere will do nothing to increase growth without changing whatever else is limiting.
In addition, there is the fact that plants tend to put on fewer stomata (pores on the bottom of the leaf they use to take up carbon dioxide) when there is more carbon dioxide in the atmosphere. Herbarium specimens exist that go back nearly 1000 years, and we can track the reduction in the stomata. Also, heat stress is a real thing, and even if they do higher photosynthesis, that could be offset by the heat stress. Rainfall changes are also important.
I hear that one a lot less since the heat waves in 2003 demonstrated that the trees in France were putting out more carbon than they were taking up, and crop yields across Europe declined.
Another thing is the shifting of agricultural zones north. The soils are not as deep and rich as the soils in the midwest, nor are they necessarily the same soils. Besides, the growing season is tied as much to the tilt of the earth as it is to temperature. Daylength is as crucial as temperature.
I always ask my students if they think the economy is complicated. They do. They think it’s the most complicated thing there is. I tell them that life and the environment make the economy look simple.